The Truth About Chemo Brain

What Is Chemo Brain?

If you or a loved one has undergone chemotherapy, perhaps you experienced a disconcerting phenomenon known as chemo brain. Also called chemo fog, this side effect induces changes in one’s thinking or cognitive function. This may manifest as forgetfulness, slower thinking, difficulty concentrating, or periods of mental confusion (fogginess). In general terms, many people say their brain is not working quite the same as it was before cancer. While cancer survivors feel better physically they may not remember where they put their keys or recall a short list of things they planned to buy at the grocery store. Chemo brain can lead to a diminished quality of life and daily functioning, with impairments affecting economic, emotional, and interpersonal aspects of one’s life. The percentage of cancer patients impacted by chemo brain varies widely, from an estimated 14% to as high as 85%.

It is believed high-dose chemo increases the risks of cognitive deficits, significantly enough to be seen on neuroimaging scans. The results of these scans imply chemo causes a diffuse, widespread injury to the brain and possibly increases sensitivity to future neurodegeneration. Chemo appears to impact the precuneus, cingulate, medial frontal, middle temporal and lateral parietal regions of the brain, as well as the hippocampus. These areas comprise what is known as the default mode network, believed to be involved in implicit learning, monitoring, and the allocation of neural resources to various cognitive processes.

Chemo brain was first reported by breast cancer survivors and is thought to impact 17% to 50% of that population. The largest study of chemo brain conducted to date found breast cancer patients had a "substantial and pervasive problem" for as long as six months after treatment. This large scale study was conducted on 581 female breast cancer patients and 364 matched healthy women (the controls) with an average age in both groups of 53. A self-reported, well-validated questionnaire called the Functional Assessment of Cancer Therapy-Cognitive Function (FACT-Cog) was used to assess cognitive impairments.

An estimated 45.2% of breast cancer patients reported a perceived decline in FACT-Cog scores in the period before and after chemotherapy, compared to 10.4% of controls during the same period. From the end of chemo to six months later, 18.4% of breast cancer patients reported "clinically meaningful perceived decline" in FACT-Cog scores compared to 11.5% of controls. Researchers stated a significant finding was that in the period prior to chemo to the six-month follow-up exam (a period spanning approximately one year), 36.5% of patients with breast cancer reported a decline in FACT-Cog scores compared to 13.6% of controls. Those with more pronounced symptoms of anxiety and depression prior to chemo experienced worse scores. Being younger and black also appeared to influence cognitive decline. Women who underwent hormone therapy or radiation treatment following chemo had similar cognitive problems to those who only received chemo.

Chemo Brain and Different Chemo Drugs

A retrospective study on 62 female breast cancer survivors who completed treatment at least two years earlier analyzed differences in cognitive impairments in those who received anthracycline-based chemo drugs, nonanthracycline-based chemo, and no chemo of any kind. Neuropsychological tests and functional magnetic resonance imaging were utilized to assess the women's cognitive status and brain connectivity.

The women in the anthracycline-based group performed significantly worse on verbal memory tasks. Connections between the precuneus and the frontal, hippocampal, and lateral parietal regions were found to be lacking in this group. Although a relatively unstudied area of the brain, the precuneus and surrounding areas have the highest resting metabolic rates in the brain. The precuneus is thought to play a role in a number of integrated tasks, including visuospatial imagery and the retrieval of autobiographical memories. Furthermore, self-reported patient outcomes of cognitive dysfunction and psychological distress were higher in both chemo groups compared to the non-chemo group.

The researchers theorize anthracycline-based chemo drugs release more pro-inflammatory cytokines, causing increased neuro-inflammation, which may be to blame for worse chemo brain. The effects of oxidative stress on the brain may also play a role. Chemo has been found to produce reactive oxygen species and reduce a patient's ability to react and clear these destructive agents, which could damage neurons.

How Long Does Chemo Brain Last?

For many patients, the symptoms of chemo brain improve over time, although they may not resolve completely. Some people may continue to experience chemo brain symptoms long after they have completed cancer treatment. Earlier research has shown the connection between the intense physical toll of chemotherapy and the short-term cognitive deficits indicative of chemo brain. A study conducted at the University of Illinois and published in the journal, "Behavioural Brain Research" analyzed the potential effects of chemo brain over a longer period of time. This research set out to determine if patients could still have cognitive deficits many months or yearslater.

While this was an animal study, the results indicated mice subjected to chemo took substantially longer to learn a given task. When the brains of the chemo-treated mice were examined, they had 26% fewer surviving hippocampal neurons created during the course of treatment, with 14% fewer hippocampal neurons generated in the three months directly after chemo. Three months for a mouse corresponds to about 10 years in human terms. If these results apply to humans, this study suggests chemo can impart long-term cognitive deficits.

Coping with Chemo Brain

It is important to be evaluated to rule out or reveal other diagnoses, such as dementia, anxiety, depression, or fatigue, all of which can also affect mental function. A neuropsychologist can devise an individualized treatment plan tailored to address a patient’s symptoms and goals. Stimulants or brain training may help some patients. Cognitive strategies or healthy lifestyle changes can also help. These include simple things like eating nutritiously, getting adequate sleep, exercising the body and mind, using calendars and reminders, minimizing distractions, avoiding or reducing stress, and sticking to regular routines as much as possible.